NPM8200 internal switches oversubscribed

Article Id:168041

Status:Published

Updated On:13-05-2017 11:14

Legacy Id:TECH244394

Products:

XOS

Issue/Introduction:

NPM8200 discards packets because the internal switches are overloadedIf a customer detects silent packet loss when traffic passes through the chassis and sees interface input errors, the internal NPM switch known as GMAC may be overloaded.

Cause:

Use the following procedure to detect whether NPM8200 internal switches are overloaded.

Each NPM8200 has 2 internal switches, which are responsible for the following physical ports:

GMAC-A: 1/1, 1/2, 1/3 and 1/4GMAC-B: 1/5, 1/6, 1/7 and 1/8

Each GMAC can handle 1GB, but each physical port has 1GB of capacity. The easiest way to detect this issue is through the swatch utility. In the output below we can see a huge amount of RxErrors in first ports (1/1 and 1/3). If the sum of the "Rx Data Rate" column for these interfaces is more than 1GB, the GMAC-A is overloaded and internal switch will drop packet silently.

To avoid that, customer should distribute the traffic using MLT to higher ports (1/5, 1/6, 1/7, 1/8) or NPMs. This is the same for GMAC-B.

In the above example, 1/1 and 1/3 are using more than 1GB together. This is causing the errors in the NPM and silent packet drops. This is an NPM8200 hardware limitation that is not present in the NPM86x0 family.

Crossbeam recommends splitting the traffic between both GMACs or more than one NPM8200, or swap the NPM8200 for an NPM86x0.

If NPM8200 internal commands are needed to corroborate this, please contact Customer Support for further troubleshooting.